There are a number of prior art methods for constructing subterranean walls and other subterranean structures. Prior-art soil-nailed walls achieve the same end of constructing a subterranean “wall”, but the method requires relatively long “nails” (deweydag rods or post tensioning tendons) to be anchored far into adjacent terrain and at relatively high cost. Such soil-nailed walls also require that one side of the “wall” be excavated to drill and insert the soil nails. Another method of forming subterranean walls in-situ is to excavate a deep trench while simultaneously filling the trench with a dense but flowable media (such as mud) to retain the soil on either side of the trench until such time as concrete placed in the trench is consolidated into the trench using a tremie and the concrete displaces the dense media. This method, called “slurry trenching”, is relatively costly and it is difficult to control construction quality since there is no access to the depths of the dense media. Typically, subterranean tanks or holding vessels are constructed by slurry trenching where ground conditions require it and then soil nailing as the excavation within this slurry trench wall system progresses. Afterwards a concrete and/or steel tank is constructed within the confines of this soil nailed and shotcreted tank cavity. (Shotcrete is a method of typically applying concrete to a generally vertical surface by projecting or “blasting” concrete onto the surface.) Subterranean tanks can also be constructed by over-excavating, then constructing a tank in the over-excavated area (as would be done above ground), and then compacting earth back around the tank. Both of these methods are relatively costly and require that excavation for the tank be done before or in conjunction with the construction of the wall. In no case with the current art can a tank or retained space be excavated for after-construction of the walls with the exception of the trench wall described above. Large retaining structures such as deep cuts for freeways and the like are typically performed using soil-nailing or with mechanical structured earth walls.
One major problem with the current art of soil nailing a large excavation is that the open face of the excavation (i.e., the exposed perimeter of the excavation below the current nailing and shotcrete level) makes it difficult to control the inflow of groundwater to the excavation before it can be sealed. Another significant disadvantage of soil nailing is that it is a costly method of stabilizing ground conditions or retained earth, especially when ground water in conjunction with non-cohesive soils requires that a slurry trench be used as a pre-stabilizer so that excavation and subsequent soil nailing can proceed. Soil nailing is also a relatively time consuming process since deep excavations often require soil nails in a closely-spaced pattern, which requires an extensive amount of drilling.
There is no prior art method for tying together or bracing caissons or cast-in-place or driven piles beneath the surface, as for example columns are analogously braced against buckling above ground with floor diaphragm beams and bracing members. Nor is there a current economic method of creating a mass or mono-caisson foundation with a plurality of caissons or piles. Nor is there currently a method of constructing foundations while simultaneously constructing the intended structure(s) upon the foundation.